The present invention relates in general to a plastic foam molding and manufacturing technique; and, in particular, the invention relates to a three-dimensional foaming flow analysis method for use in the foam-molding of a foam part, such as a heat insulator and a shock absorber, to be used in a refrigerator, as a building material and in an automobile.
JP-A-2001-318909 and JP-A-2003-91561 disclose an analysis program which employs a function of density control in the manufacture of a foaming material using time as a variable, whereby a foaming behavior having a density decreasing with time can be analyzed.
According to JP-A-2001-318909, in particular, the entire body of foaming material is regarded as having a uniform density, and the density is a density calculated on the basis of the elapsed time after the foaming material first exits from a nozzle, which outputs a foaming material obtained by beating a foaming ingredient.
JP-A-2003-91561 discloses that a foaming flow analysis can be performed on a foaming material by using a function based on the fact that the density of the foaming material depends on a change in the thickness, in addition to the technique disclosed in JP-A-2001-318909.
In an actual manufacturing process, a foaming material near the outlet of a nozzle has a substantially constant density which does not change with time.
The influence of the foaming material that is first output from a nozzle decreases the liquidity of the foaming material subsequently output from the nozzle. Therefore, while the result of the foaming flow analysis up to about one second may be usable as an approximate value, the result of the foaming flow analysis for a longer period of time may be significantly different from the real value. For these reasons, the analysis according to JP-A-2001-318909 and JP-A-2003-91561 has a low precision.
JP-A-2003-91561 further discloses that the densities of foaming resins are displayed in groups. However, since the grouping is based on the thicknesses of the foaming resins, similar outputs to those of JP-A-2001-318909 are disadvantageously given an equal thickness.